Painful toxins acting at TRPV1.

Many plant and animal toxins cause aversive behaviors in animals due to their pungent or unpleasant taste or because they cause other unpleasant senstations like pain. This article reviews the current state of knowledge of toxins that act at the TRPV1 ion channel, which is expressed in primary sensory neurons, is activated by multiple painful stimuli and is thought to be a key pain sensor and integrator. The recent finding that painful peptide "vanillotoxin" components of tarantula toxin activate the TRPV1 ion channel to cause pain led us to survey what is known about toxins that act at this receptor. Toxins from plants, spiders and jellyfish are considered. Where possible, structural information about sites of interaction is considered in relation to toxin-binding sites on the Kv ion channel, for which more structural information exists. We discuss a developing model where toxin agonists such as resiniferatoxin and vanillotoxins are proposed to interact with a region of TRPV1 that is homologous to the "voltage sensor" in the Kv1.2 ion channel, to open the channel and activate primary sensory nerves, causing pain.